Appliance that's uninteresting about to be returned (5)
I believe the answer is:
dryer
'appliance' is the definition.
(dryer is a kind of appliance)
'uninteresting about to be returned' is the wordplay.
'uninteresting' becomes 'dry' (I've seen this before).
'about' becomes 're' (regarding**).
'to be returned' says the letters should be written in reverse (I've seen 'is returned' mean this).
're' written backwards gives 'er'.
'dry'+'er'='DRYER'
'that's' acts as a link.
(Other definitions for dryer that I've seen before include "Water extractor" , "It removes moisture" , "one's found in launderette" , "Try to obtain (something from someone)" , "tumbler, perhaps" .)